Motilin is a physiologically active peptide occurring in the mammalian blood and is known to be capable of activating peristalsis of the intestine (W. Y. Chey and K. Y. Lee, Clinics in Gastroenterology, 3, 645 (1980)). Laparotomized patients show decreased motilin concentrations in the blood, and is known that the return of postoperative blood motilin concentrations to a normal level is correlated with the restoration of peristaltic movement of the intenstine in such patients and that post-operative administration of motilin results in activated peristalsis of the intestine.
Natural motilin can be obtained by extraction from animal organs but in insufficient quantities. Therefore, motilin in current use is mostly a product of chemical peptide synthesis. However, this chemical product is necessarily expensive since motilin is a relatively long chain peptide composed of 22 amino acid residues. Accordingly, it is desired that a substance having motilin activity be supplied at low cost and in large quantities.
The 13th amino acid of motilin is Met, which is readily oxidizable. Oxidation of Met to the sulfoxide form results in decreased motilin activity (M. Fujino et al., Chem. Pharm. Bull., 26, 101 (1978)).